Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
# ans = 全白マス数 - 最短距離のマス数

H,W=map(int,input().split())
grid=[None]*H
white=0
for i in range(H):
  grid[i]=input()
  white+=grid[i].count(".")
  
from collections import deque
q=deque()
q.append([0,0,0])

seen=[[False for i in range(W)] for j in range(H)]

while q:
  v=q.popleft()
  y=v[0]
  x=v[1]
  p=v[2]
  if grid[y][x]=="#" or seen[y][x]:
    continue
  if y==H-1 and x==W-1:
    print(white-(p+1))
    break
  seen[y][x]=True
  if y-1>=0:
    q.append([y-1,x,p+1])
  if y+1<H:
    q.append([y+1,x,p+1])
  if x-1>=0:
    q.append([y,x-1,p+1])
  if x+1<W:
    q.append([y,x+1,p+1])
else:
  print(-1)